Nasa released a low resolution map which they say represents the most likely track the satellite took in its last minutes.

It came up from the south west near Fiordland and raced along the west coast before passing over Northland and carrying on over the Pacific to cross over most of Tonga before breaking up at 14.1 degrees south latitude and 170.2 west – almost exactly over Pago Pago, American Samoa.

Debris continued north and east falling in an area which includes the New Zealand's three atoll territory of Tokelau – home to 1200 people – and American Samoa's Swains Atoll.

Most of the debris is believed to have hit the sea south of Kiribati’s Christmas or Kiritimati Island, home to around 5000 people.

Today Nasa say experts believe about two dozen metal pieces from the bus-sized satellite fell over a 800km span.

Scientists who track space junk couldn't be happier with the result.

"That's the way it should be. I think that's perfect," said Bill Ailor, director of the Centre for Orbital and Re-entry Debris Studies at the Aerospace Corp. "It's just as good as it gets."

On Saturday, scientists said it was possible some pieces could have reached northwestern Canada and claims of sightings in Canada spread on the Internet. But Nasa said today that new calculations show it landed several minutes earlier than they thought, changing the debris field to an entirely different hemisphere.

"It just shows you the difference that 10 or 15 minutes can make," said Harvard University astrophysicist Jonathan McDowell, who tracks man-made space objects. On Saturday, he noted, "We were talking about, `Wow, did it hit Seattle?'"

Nasa won't say how it knows the climate research satellite came in earlier, referring questions to the US Air Force space operations centre, which tracked the re-entry. Air Force officials have so not been available for comment about that issue.

McDowell theorises that a Defence Department satellite designed to track missile launches helped pinpoint where the Upper Atmosphere Research Satellite returned to Earth.

After UARS was launched in 1991, Nasa and other space agencies adopted new procedures to lessen space junk and satellites falling back to Earth. So Nasa has no more satellites as large as this one that will fall back to Earth uncontrolled in the next 25 years, according to Nasa orbital debris chief scientist Nicholas Johnson.

But other satellites will continue to fall. Late in October, or early in November, a German astronomy satellite is set to plunge uncontrolled back to Earth. While slightly smaller than UARS, the German satellite is expected to have more pieces survive re-entry, said McDowell, who worked on one of the instruments for it.

The German ROSAT satellite was launched in 1990, died in 1998, and weighs 2½ tons. The German space agency figures 30 pieces weighing less than 2 tons will survive re-entry. Debris may include sharp mirror shards.

The German space agency puts the odds of somebody somewhere on Earth being hurt by its satellite at 1-in-2000 - a slightly higher level of risk than was calculated for the Nasa satellite. But any one individual's odds of being struck are 1-in-14 trillion, given there are seven billion people on the planet.